This application is based on and incorporates herein by reference Japanese Patent Application Nos. 2000-48812 filed on Feb. 25, 2000, and 2000-75824 filed on Mar. 17, 2000.
1. Field of the Invention
The present invention relates to a fluid injection nozzle having an injection port plate, and to a fuel injection nozzle for injecting a fuel into an internal combustion engine.
2. Description of Related Art
In the prior art, there has been known a fuel injection valve in which a thin injection port plate having a plurality of injection ports is arranged on the fuel downstream side of a valve unit formed of a valve member and a valve seat so that the fuel is injected from the individual injection ports. As shown in FIGS. 13A and 13B, it is customary that the injection ports 301 formed in the injection port plate 300 are given a constant diameter from the injection port inlet to the injection port outlet. Fuel, flowing into the injection port 301 having the constant diameter, does not spread along an injection port inner circumference 302 and is injected as a liquid column. The liquid column fuel is hardly atomized. In U.S. Pat. No. 4,907,748, on the contrary, there is disclosed an injection port plate in which the injection ports are radially enlarged to diverge toward the fuel downstream side.
However, the diverging injection ports, as disclosed in U.S. Pat. No. 4,907,748, are diverged substantially homogeneously toward the fuel downstream side so that the fuels to pass through the injection ports fail to contact with the injection port inner faces of the injection port plate forming the injection ports and are injected in liquid columns without being spread. This makes it difficult to atomize the fuel sufficiently.
In another prior art, there has been proposed an electromagnetic type fuel injection valve (JP-A-9-14090 or the like) which is provided with a mechanism (e.g., an orifice plate 406) for promoting the atomization of a fuel spray to be injected at a good timing to the vicinity of the intake valve of the internal combustion engine such as a gasoline engine.
This electromagnetic type fuel injection valve is constructed, as shown in FIGS. 22, 23A and 23B, to include: a cylindrical valve body 403 having an opening 401 at the central portion of its leading end and a valve seat 402 on the upstream side of the opening 401; a needle valve 405 housed slidably in the valve body 403 and having a seat portion 404 on the outer circumference of its leading end portion for abutting against the valve seat 402; and the orifice plate 406 arranged on the leading end face of the valve body 403 for shutting the opening 401. In the orifice plate 406, moreover, there are formed therethrough circular injection ports (orifices) 408 which are inclined at a predetermined angle A (degrees) from their fuel inlets to their fuel outlets backward to the upstream side with respect to the fuel flow direction of a fuel passage 407.
In the electromagnetic type fuel injection valve of the prior art, however, in the fuel passage 407 formed between the leading end face of the needle valve 405 and the passage wall face of the orifice plate 406, the fuel having flown in from between the valve seat 402 and the seat portion 404 flows along the passage wall face of the orifice plate 406 toward the fuel inlet of the orifice 408 and then into the orifice 408.
Here, as shown in FIGS. 23A and 23B, a liquid column portion 409 is established in the flow of the fuel in the orifice 408. As the capacity of this liquid column portion 409 of the fuel flow is the larger, the surface area of the liquid column portion 409 of the fuel flow is the smaller so that the area to contact with the air is reduced to prevent the cleavage. As a result, there arises a problem to deteriorate the effect to promote the atomization of the fuel spray which is injected to the vicinity of the intake valve from the orifice 108 formed through the orifice plate 406.
An object of the invention is to provide a fluid injection nozzle for atomizing a fluid spray.
According to a first aspect of the present invention, the first intersection line and the second intersection line are inclined in the same direction as the injection port axis, and xcex81 less than xcex82, if the first inclination angle to be formed by the first intersection line with the center axis of the injection port plate is designated by xcex81 and if the second inclination angle to be formed by the second intersection line with the center axis of the injection port plate is designated by xcex82. The injection port is diametrically enlarged on the injection port axis toward the fluid outlet side so that the area of the injection port circumference is made larger than that of the injection port of an equal diameter. Moreover, the fuel to flow into the injection port never fails to contact with the injection port inner circumference containing the first intersection line so that it is spread while being guided. Therefore, the fluid to be injected from the injection port does not become the liquid column but is spread into a liquid film so that it is easily atomized.
According to a second aspect of the present invention, the injection port is arranged in plurality so that the injection rate for one injection port is reduced to reduce the injection port diameter. Therefore, it is possible to promote the atomization of the fluid spray.
According to a third aspect of the present invention, the fluid chamber formed just above the fluid inlets of the injection ports is diametrically larger than the fluid downstream side open end formed by the inner circumference. Moreover, the injection ports are opened at their fluid inlets in the inner circumference and the outer circumference of the virtual envelope on which the virtual plane extended from the inner circumference toward the fluid downstream side intersects the injection port plate. The fluid flows from the outer circumference to the inner circumference of the injection port plate into the inner injection ports positioned in the inner circumference side of the virtual envelope, and the fluid flows from the inner circumference to the outer circumference of the injection port plate into the outer injection ports positioned in the outer circumference side of the virtual envelope. The fluids flow in the leaving directions into the inner injection ports and the outer injection ports so that the fluid spray from the inner injection ports and the fluid spray from the outer injection ports are prevented from overlapping just below the injection ports. Therefore, the atomization of the fluid spray is promoted.
According to a fourth aspect of the present invention, an injection port is so formed through the injection port plate from its fuel inlet to its fuel outlet that it is inclined at a predetermined angle backward to the upstream side with respect to the fuel flow direction of the fuel passage, and on the port wall face from the fuel inlet to the fuel outlet of the injection port, there are formed two curvature circle portions which have their centers of curvature on the center axis of the injection port and which are directed backward to the upstream side with respect to the flow direction of the fuel passage.
As a result, in the fuel passage formed between one end face of the needle valve and the passage wall face of the injection port plate, the fuel having flown in from between the valve seat and the seat portion flows along the passage wall face of the injection port plate toward the fuel inlet of the injection port and then into the injection port. At this time, there is established in the fuel flow in the injection port the liquid column portion, which is dispersed along one of the two curvature circle portions and injected from the fuel outlet of the injection port. As a result, the surface area of the liquid column portion of the fuel flow in the injection port to increase the area of contact with the air so that the cleavage of the liquid column portion is promoted. Therefore, it is possible to suppress the deterioration in the effect to promote the atomization of the fuel spray.
According to a fifth aspect of the present invention, a first curvature circle portion is formed on the center axis side of the fuel injection valve and having a predetermined radius of curvature having the center of curvature on the center point of a circle of curvature, and a second curvature circle portion is formed on the side opposed to the center axis side of the fuel injection valve and having a radius of curvature having the center of curvature on the center point of a circle of curvature and substantially identical to the first curvature circle portion. As a result, the liquid column portion of the fuel flow in the injection port is dispersed along the first one of the two curvature circle portions and is injected from the fuel outlet of the injection port.
According to a sixth aspect of the present invention, a plurality of injection ports are arranged on an imaginary line of a single circle on the center axis of the injection port plate.
According to a seventh aspect of the present invention, a plurality injection ports are arranged on imaginary lines of double circles on the center axis of the injection port plate.